1. Field of the Invention
The present invention relates to a method of folding a sheet, comprising feeding a sheet to be folded to a folding unit, repeatedly folding the sheet with the folding unit, thereby creating a folded package, and discharging at least a part of the folded package from the folding unit.
The present invention further relates to a folding apparatus for carrying out the method of the invention, in particular a folding apparatus for wide format printing systems.
2. Background of the Invention
Preferably, the folding unit is adapted for forming at least one fold at a not weakened position of the sheet, i.e. at a not previously folded, perforated or otherwise weakened position. Preferably, in the folding step, at least one fold is formed at a not weakened position of the sheet. Thus, the method is suitable for folding a printed sheet at previously unweakened positions. This is in contrast to a method of folding a paper web at pre-weakened fold lines as described in U.S. Pat. No. 5,279,536.
The sheet may be a printed sheet, i.e. a sheet printed in a printing apparatus, e.g. a printer or copier.
U.S. Pat. No. 5,989,174 describes a zig-zag folding method and apparatus wherein a folded web is continuously discharged from a folding station and collected on a collection shelf. The folding apparatus requires a complicated structure which is prone to inaccurate folding. A step of discharging the collected web from the collection shelf is not disclosed.
From U.S. Pat. No. 5,131,640, a method for processing web material is known, wherein, in a folder/cutter, the web is folded to produce a zig-zag pattern and cut into folded sheets. The folded sheets are discharged from the folder/cutter and are stacked on an output stack. The structure of the folder/cutter is not described, and a step of discharging the stack of folded sheets from the output stack is not disclosed.
GB 2 196 944 describes folding a continuous running paper web in zig-zag formation. A completed stack is moved laterally away from the stacking station so that a topmost panel of the stack or a lowermost panel of the remainder of the pile is unfolded, and the web is broken between such panels by tearing it or severing it.
EP 1 842 818 discloses a folding method and apparatus of the type mentioned initially. After forming the folds on a folding cylinder, the created folded package is unloaded from the folding cylinder and discharged by rotating the folding cylinder. The folding apparatus produces a precisely folded package while having a simple and compact configuration. However, the folding length (i.e., the length of the sheet that can be folded) is limited due to the structure of the folding unit, because with an increasing length of the sheet, the number of the folds and thus the number of the layers in the folded package held on the folding cylinder increases, and folding tolerances increase. A typical limit for the length of the sheet, e.g. a continuous paper web, is six meters.